Thermostatically controlled immersion heater



J. J. FINN May 19, 1964 THERMOSTATICALLY CONTROLLED IMMERSION HEATER Filed April 20, 1961 Ill-I r"""'" Li TmE mmvrm JOHN J. Fnv/v United States Patent A 3,134,00 THERMOSTATICALLY CONTROLLED IMMERSION HEATER John .I. Finn, Rocirville, Md, assignor to Electra-Therm, Inc., Silver Spring, Md. Filed Apr. 20, 1961, Ser. No. 104,398

Claims. (Cl. 219-38) This invention relates to electric heaters, and more particularly to an electric immersion heater of the thermostatically controlled type. I

A mainobject of the invention is to provide a novel and improved thermostatically controlled electric immersion heater which is simple in construction, which is easy to assemble, and which provides a sealed mechanical connection between the supporting flange of the heater and the temperature-responsive element thereof.

A further object of the invention is to provide an improved thermostatically controlled electrical immersion heater assembly which is inexpensive to manufacture, which is mechanically rugged, and which is relatively compact in size.

, A still further object of the invention is to provide an improved thermostatically controlled electrical immersion heater assembly which provides a thoroughly sealed and mechanically strong connection between the thermostat element thereof and the supporting flange of the assembly without requiring the use of threaded bushings or other threaded elements, whereby the assembly may be efiiciently and economically manufactured.

Further objects and advantages of the invention will become apparent from the following description and claims, and from the accompanying drawings, wherein:

FIGURE 1 is a side elevational view, partly in vertical cross-section, of an improved thermostatically controlled electric immersion heater assembly constructed in accordance with the present invention.

FIGURE 2 is an end elevational view of the heater assembly of FIGURE 1, taken on the line 22 of FIG- URE 1.

FIGURE 3 is an enlarged fragmentary elevational view, partly in vertical cross-section, of the thermostat element and its supporting conduit as employed in the assembly of FIGURES 1 and 2.

FIGURE 4 is a transverse cross-sectional view taken substantially on the line 44 of FIGURE 3.

Referring to the drawings, 11 generally designates an immersion heater assembly according to the present invention. The assembly 11 comprises a generally square main supporting flange 12 adapted to be sealingly secured over an aperture in the wall of a tank or similar vessel containing liquid to be heated. The flange is formed with a circular boss 13 around which a suitable sealing face plate or gasket, not shown, is adapted to be positioned. Suitably secured in and extending through the flange 12 at the boss 13 are the legs of a plurality of U-shaped heating elements of the type comprising tubular metal sheaths containing coiled resistance wires with compacted insulating heat-conductive material filling the spaces in'the tubular sheaths, the ends of the wires being connected to suitable terminals provided at the ends of said legs. Said terminals extend into a spacer sleeve 14 secured between the flange 12 and a control box 15. The control box 15 contains a conventional adjustable thermostatically controlled switch assembly through which connection is made from the power supply lines to the terminals of the heating elements, the switch assembly including a temperature setting knob 16 and a reset button 17, whereby the switch assembly may be reset for operation subsequent to cooling after the heat-responsive controls of the switch have opened as a result of the rise in temperature in the as- 1 3,134,008 Patented May 1964 sociated tank to a value higher than a predetermined amount. I p p I In the typical assembly illustrated, there are a pair of parallel heating elements 18, 18 and a third heating element 19 arranged transverse to and disposed within the parallel U-shaped heating elements 18, 18.

The thermostatic switch in box 15 is provided with a capillary tube 20 connected to an elongated temperature sensing bulb 31 whichis mounted on the uppermost leg of the vertical element 19 by means of a pair of spaced generally U-shaped metal clips 21, 21 which receive the bulb and which are provided with opposing arcua-te concave legs 22 embracing the upper leg of element 19 and clamped thereto by fastening screws 23.

The capillary tube 20 extends axially through a generally cylindrical sheet metal sleeve 24 secured in a central aperture 25 provided therefor in flange 12. The sleeve 24 is brazed to the opposite surfaces of the flange 12 as shown at 25 and 2610 define a liquid-tight connection therewith. The tube 20 is sealingly secured axially in the sleeve by a mass of suitable potting compound 27,

t such as epoxy resin material, capable of withstanding high temperature and pressure. A radially split flexible retaining washer 28 of fibre, or other suitable flexible material, is frictionally engaged in one end portion of sleeve 24 to'aid in centering the tube 20 therein and to retain the potting compound when it is introduced into the sleeve in its liquid condition. An annular inwardly directed corrugation or crimp 30 is provided in the intermediate portion of sleeve 24, serving as an anchoring means for the potting compound 27 afiter it has hardened.

The potting compound 27 provides a liquid and pressure-tight seal between the sleeve 24 and the capillary tube 20, and supports the capillary tube in centered axial position in the sleeve. In prior construction, it has been necessary to provide relatively complicated and expensive sealing glands between the capillary tube and the flange, and it has been necessary to form internal threads in the aperture in the flange through which the tube passes in order to threadedly mount the outer bushings of the sealing glands. The present invention eliminates the necessity of providing threaded openings in the flange and of employing expensive sealing gland assemblies.

While a specific embodiment of an improved thermostatically controlled electric immersion heater assembly has been disclosed in the foregoing description, it will be understood that various modifications within the spirit of the invention may occur to those skilled in the art. Therefore it is intended that no limitations be placed on the invention except as defined by the scope of the appended claims.

What is claimed is:

1. A thermostatically controlled electrical heating unit comprising a supporting flange, a heating element mounted on said flange, a thermostat bulb mounted adjacent the element, a sleeve member open at its ends and rigidly secured in and extending through the flange in watertight relationship therewith, a capillary tube connected to the bulb and extending through the sleeve member, said bulb being outside the sleeve member and being arranged to be in direct contact with the fluid being heated by said heating element, a mass of relatively heat resistant potting compound in the sleeve member surrounding the tube and sealing the tube with respect to said sleeve member, and a thermostatic control means mounted on the flange and connected to the thermostat bulb by said capillary tube, said control means being operatively associated with the heating element to control the latter.

2. A thermostatically controlled electrical heating unit comprising a supporting flange, a heating element mounted on said flange, a thermostat bulb mounted adjacent the element, a sleeve member open at its ends and rigidly secured in and extending through the flange in watertight relationship therewith, a capillary tube connected to the bulb and extending through the sleeve member, said bulb being outside the sleeve member and being arranged to be in direct contact with the fluid being heated by said heating element, a mass of heat-resistant potting compound in the sleeve member surrounding the tube and sealing the tube with respect to the sleeve member, an inwardly projecting indentation in the sleeve member to anchor the potting compound, and a thermostatic control means mounted on the flange and connected to the thermostat bulb by said capillary tube, said control means being operatively associated with the heating element to control the latter.

3. A thermostatically controlled electrical heating unit comprising a supporting flange, a heating element mounted on said flange, a thermostat bulb mounted adjacent the element, a sleeve member open at its ends and rigidly secured in and extending through the flange in water-tight relationship therewith, a capillary tube connected to the bulb and extending axially through the sleeve member, said bulb being outside the sleeve member and being arranged to be in direct contact with the fluid being heated by said heating element, a mass of substantially heatresistant potting compound in the sleeve member surrounding the tube and sealing the tube with respect to the sleeve member, an inwardly projecting annular corrugation formed in the sleeve member to anchor the potting compound, and a thermostatic control means mounted on the flange and connected to the thermostat bulb by said capillary tube, said control means being operatively associated with the heating element to control the latter.

4. A thermostatically controlled electrical heating unit comprising a supporting flange, a heating element mounted on said flange, a thermostat bulb mounted adjacent the element, a sleeve member open at its ends and rigidly secured in and extending through the flange in watertight relationship therewith, a capillary tube connected to the bulb and extending through the sleeve member, said bulb being outside the sleeve member and being arranged to be in direct contact with the fluid being heated by said heating element, an annular centering washer in the sleeve member surrounding the tube, a mass of heat-resistant potting compound in the sleeve member surrounding the tube and sealing the tube with respect to the sleeve member, and a thermostatic control means mounted on the flange and connected to the thermostat bulb by said capillary tube, said control means being operatively associated with the heating element to control the latter.

5. A thermostatically controlled electrical heating unit comprising a supporting flange, a heating element mounted on said flange, a thermostat bulb mounted adjacent the element, a sleeve member open at its ends and rigidly secured in and extending through the flange in water-tight relationship therewith, a capillary tube connected to the bulb and extending through the sleeve member, said bulb being outside the sleeve member and being arranged to be in direct contact with the fluid being heated by said heating element, an annular centering washer in the sleeve member surrounding the tube, a mass of heat-resistant epoxy potting compound in the sleeve member surrounding the tube and sealing the tube with respect to the sleeve member, an inwardly projecting annular corrugation formed in the sleeve member to anchor the potting compound, and a thermostatic control means mounted on the flange and connected to the thermostat bulb by said capillary tube, said control means being operatively associated with the heating element to control the latter.

References Cited in the file of this patent UNITED STATES PATENTS 1,141,576 Ovington June 1, 1915 1,930,551 Blashfield Oct. 17, 1933 2,217,595 Morgan et al. Oct. 8, 1940 

1. A THERMOSTATICALLY CONTROLLED ELECTRICAL HEATING UNIT COMPRISING A SUPPORTING FLANGE, A HEATING ELEMENT MOUNTED ON SAID FLANGE, A THERMOSTAT BULB MOUNTED ADJACENT THE ELEMENT, A SLEEVE MEMBER OPEN AT ITS ENDS AND RIGIDLY SECURED IN AND EXTENDING THROUGH THE FLANGE IN WATERTIGHT RELATIONSHIP THEREWITH, A CAPILLARY TUBE CONNECTED TO THE BULB AND EXTENDING THROUGH THE SLEEVE MEMBER, SAID BULB BEING OUTSIDE THE SLEEVE MEMBER AND BEING ARRANGED TO BE IN DIRECT CONTACT WITH THE FLUID BEING HEATED BY SAID HEATING ELEMENT, A MASS OF RELATIVELY HEAT RESISTANT POTTING COMPOUND IN THE SLEEVE MEMBER SURROUNDING THE TUBE AND SEALING THE TUBE WITH RESPECT TO SAID SLEEVE MEMBER, AND A THERMOSTATIC CONTROL MEANS MOUNTED ON THE FLANGE AND CONNECTED TO THE THERMOSTAT BULB BY SAID CAPILLARY TUBE, SAID CONTROL MEANS BEING OPERATIVELY ASSOCIATED WITH THE HEATING ELEMENT TO CONTROL THE LATTER. 